.header-nav {
  float: left;
}

.user-info-box {
  float: right;
  position: relative;
}

.user-info-box img {
  width: 35px;
  height: 35px;
  border-radius: 50%;
  border: 3px solid #fff;
  margin-right: 10px;
  vertical-align: middle;
}

.header-menu {
    position: absolute;
    top: 65px;
    left: 0;
    border: 1px solid #d1dbe5;
    padding: 5px 0;
    background-color: #fff;
    z-index: 100;
    text-align: center;
    min-width: 100%;
    box-shadow: 0 2px 4px 0 rgba(0,0,0,.12), 0 0 6px 0 rgba(0,0,0,.04);
    opacity: 0;
    height: 0;
    transition: .5s;
    overflow: hidden;
}

.user-info-box:hover .header-menu {
  opacity: 1;
  height: 60px;
}

.header-menu li {
  height: 50px;
  color: #000;
}